1. Field of Invention
The present invention relates to a digital image processing method, and more particularly to a false color suppression method for a digital image.
2. Related Art
For human eyes, the so-called color is actually the reflected visible light after an object absorbs the light of the most of the spectrum in the light ray. For example, after the green leaf absorbs the light of the most of the spectrum in the light ray, the human eyes receive the reflected green visible light, so as to assume the green leaf seen by people. In the nature, if the red light, the green light, and the blue light are mixed based on a certain proportion, various different colors are obtained. In fields related to computer, three primary colors of red, green, and blue are used as the color mixing reference. For example, RGB is a method of encoding the color, in which several bytes are used to express the intensity of the three primary colors of red, green, and blue, thereby expressing various different colors. The color gamut space (YUV), also called TV system color gamut (YCrCb) is also a manner of expressing the color, in which “Y” expresses the luminance of the digital image, and “U” and “V” express the chrominance, similar to the color difference (Cr and Cb) in the TV system color gamut. The principle is also applied to the digital camera, and the color light is received through photosensitive elements such as CCD, so as to generate the digital image. During using of the digital camera, usually when it is found that the light source is too dark or when the night scene is shot, the photosensitivity is improved, such that the shot digital image achieves a proper luminance. However, when the photosensitivity is improved, the noise and the false color occur. The so-called false color is the unnatural color occurring on the position in the digital image, on which originally the color shade should be same, for example, when shooting the clothes with the blue cloth, the obtained image has red wave stripes.
In order to make the image shot by the digital camera have the imaging effect of certain quality under the high photosensitivity, the false color suppression technique becomes an important topic. The recent false color suppression techniques are classified into two types. For one type, it is necessary to find out the texture and the detail of the luminance or the chrominance of the image through complicated analysis, and then obtain better suppression effect through a larger equivalent mask. If the equivalent mask is not large enough, the suppression effect is limited. For the other type, the suppression of intensity of the false color is achieved by sacrificing a part of the chrominance of the image. The human eye visual sense is sensitive to the false color on the chrominance approaching the grey scale, so in the method, mostly the color approaching the grey scale is suppressed to approach the grey scale, such that the visual effect of the false color is distinctly reduced. The two false color suppression methods have respective advantages and disadvantages. In other words, the recent false color suppression techniques cannot achieve a balance between the image process complexity and sacrificing of the chrominance.